1. Field of the Invention
The present invention relates to a display processor for a raster display system for displaying video information such as alphanumeric and graphic patterns on the face of a cathode-ray tube (CRT).
2. Description of the Prior Art
Demands such as resolution on computer-display systems are very versatile and vary from one user to another. For instance, it is desired to display simultaneously a plurality of pages of video information (to be referred to as "display files" for brevity in this specification) so that a plurality of graphic patterns can be displayed in mutually superimposed relationship on the same face of a cathode-ray tube. However, the number of display files to be simultaneously displayed varies from one user to another. As a result, various types of computer display systems must be specially designed and fabricated depending upon the demands of users.
Prior art systems for displaying a plurality of display files in mutually superimposed relationship (to be referred to as "the superimposed-picture display system" for brevity in this specification) are in general large in size and complex in construction. Furthermore, if such display systems are custom-tailored, their costs would become prohibitively expensive because each system must be specially designed and fabricated.